None.
The present invention relates to powered brush cutters, string trimmers, etc, hereafter referred to as cutting devices. In particular, the present invention relates to a safe, compact and streamlined, powered cutting device which is maneuverable in the manner of a wheelbarrow, brush cutter, or stick edger.
Hitherto, powered cutting device have been able to be divided into several categories. The first is a multi-wheeled carriage which is self-supporting on its wheel and which is pushed along its intended path. A known member of this class is essentially a conventional domestic lawn mower type but with a cutting element of nylon or like filaments rotating in a horizontal plane. Another member of this class is the 3 (or 4) wheel lawn edger which can pivot its cutter blade 90 degrees to a horizontal position. The best known category is a hand held device which does not have any ground engaging wheels and which is carried by the operator. The best known of these devices are the various types of brush cutter (or string trimmer) devices.
The brush cutter type of device generally includes a nylon filament as a cutting element. This cutting element is attached to a cutter head which is set at one (lower) end of a long drive shaft. The drive shaft is carried by the operator at an angle of approximately 35xc2x0 to 45xc2x0 to the horizontal. The shaft has an engine at its other (upper) end with the engine mostly situated behind the operator and in some other cases beside the operator. The cutter head rotates about a substantially horizontal plane in normal use and is intended, for example, to trim grass growing adjacent tree trunks, to mow vegetation, mostly grass and/or weeds in small and/or awkward areas, and the like. Therefore, it is necessary for such an apparatus to be completely carried in a generally out of balance position. Therefore, it is both difficult and tiring to use.
As a consequence, any health problem of the operator, such as common backache, can be exacerbated by the stooped and unnatural position which the operator is obligated to adopt. The fatigue of the operator is further increased by the need to actually carry, and therefore support the entire weight of, the device during its operation.
Another known device is a stick edger which is constructed similarly to a brush cutter but with a cutting blade rotating in a fixed vertical plane and with a small wheel attached to the blade cover.
It is also known for some prior art cutting devices to be fitted with one or several rollers attached to the device near the cutter head or for the device to be fitted to a dolly. Some of these devices still have their engine alongside, or behind, the operator, so the majority of the weight is still supported by the operator with the same generally awkward stance and movement as described above. One hand of the operator carries the majority of weight whilst the other hand of the operator guides the dolly. Again, this can cause stooping, which exacerbates any back problem. Back problems are a major source of health insurance injury claim and are a major source of injury for manual laborers. In all instances, these dollies, or wheel mounted arrangements, suffer the problem of lack of maneuverability. As a consequent, they are all difficult and awkward to use.
Various prior art devices in the form of a wheeled dolly have been proposed in order to support such brushcutter devices. The following U.S. patents are typical of such devices: U.S. Pat. No. 4,182,100 (Letter); U.S. Pat. No. 4,442,659 (Enbusk); U.S. Pat. No. 4,531,350 (Huthmacher); U.S. Pat. No. 4,803,831 (Carmine); U.S. Pat. No. 4,879,869 (Buckendorf, Jr.); U.S. Pat. No. 4,894,916 (Nimz et al.); U.S. Pat. No. 4,922,694 (Emoto); U.S. Pat. No. 4,936,886 (Quillen); U.S. Pat. No. 5,029,435 (Buchanan); and U.S. Pat. No. 5,095,687 (Andrew et al.).
A further problem to be considered is the restrictions to be placed on small two-stroke (two-cycle) engines because of the pollution such engines create over and above that created by four-stroke engines. As a consequence, the light weight two-stroke power units currently used in brushcutters and similar devices are likely to be banned in some jurisdictions in the future for anti-pollution reasons. The engineering result of this is that commercially acceptable power units are henceforth likely to be restricted to four-stroke internal combustion engines and electric motors, both of which are substantially heavier than two-stroke engines. It follows, therefore, that in the future those brush cutters in which the operator carries the weight of the apparatus will become impractically heavy.
The wheeled carriage class of lawn edger typically has three (or sometimes four) wheels arranged so as to enable the edger to be free standing, with upstanding handles, and also self-supporting on its wheels. Some of these edgers can swivel their vertical blades to a horizontal plane to trim grass and vegetation in a horizontal manner. The device is pushed in a manner analogous to that of a lawn mower. Because these self-supporting 3 and 4 wheeled carriage grass edgers have a long wheel base to self-support the apparatus, when pushed (forward) their natural track is straight. Therefore, to push around a curve is difficult with the operator having to xe2x80x9cbouncexe2x80x9d, or reciprocate, or drag, the apparatus around, to try to approximate the desired curve which the non-steerable carriage wheels will not follow.
These prior art lawn edgers, to cut horizontally, have mechanisms that take the form of a tiltable axis of rotation of the cutter, and a V-belt drive which is able to accommodate the necessary twisting required whilst still transmitting power. The power unit remains untilted. Whilst such arrangements are functional, the devices are heavier, more complicated and more expensive. In addition, the (often exposed) V-belt drives are dangerous.
Examples of prior art wheeled carriage devices which have attempted to deal with this problem include: U.S. Pat. No. 2,680,945 (Reed); U.S. Pat. No. 2,791,875 (Faas); U.S. Pat. No. 2,847,813 (Hansen, Jr. et al.); U.S. Pat. No. 2,855,742 (Cooper); U.S. Pat. No. 3,090,186 (Dykes); U.S. Pat. No. 3,193,996 (Wellborn); U.S. Pat. No. 3,490,213 (Pinto); U.S. Pat. No. 3,743,028 (McCloud); U.S. Pat. No. 4,962,631 (Braun et al.); U.S. Pat. No. 5,156,217 (Hirata et al.); and U.S. Pat. No. 5,165,485 (Fujikawa et al.). The MASPORT (Registered Trade Mark) model 6002 DLX which is commercially available in the USA also has a blade tilting arrangement. All of these xe2x80x9cheavy dutyxe2x80x9d wheeled edgers are heavy and bulky, difficult to transport, cannot fit into a boot or trunk of even a large car, and require a great deal of room for storage.
Another example of a prior art device in which the cutting blades are able to be tilted out of the vertical plane is provided by U.S. Pat. No. 2,970,419 (Lieberman). This device enables a cut to be achieved both in a horizontal plane and in a vertical plane. When cutting in a horizontal plane the device is supported by a pair of wheels 40, and when cutting in a vertical plane the device is supported by a roller 54. U.S. Pat. No. 2,672,002 (Nelson) discloses a somewhat similar device which, when cutting in the vertical plane, is supported by single wheel 15 in front of the cutter blade, but when cutting in the horizontal plane is supported by a skid bar 28. Because of the skid bar 28, it is necessary to xe2x80x9cshove or pushxe2x80x9d the device in the direction of the skid bar 28 utilizing a handle of which only the stem 31 is illustrated. The handle is said to have xe2x80x9cany desirable cross-headxe2x80x9d and, therefore, is presumably generally T-shaped in configuration.
U.S. Pat. No. 2,621,463 (Skillman) discloses a similar arrangement in which the device is supported in both cutting actions by a roller 11 having a substantial axial extent. Again, the cutting blades are able to be pivoted so as to cut in either a horizontal plane or a vertical plane. U.S. Pat. No. 2,632,990 (Stricklen et al.) discloses a single wheeled carriage device with a free standing and upstanding handle. The carriage has supporting shoes or skids 20 to maintain the carriage upright in the rest position. The devices is able to cut either vertically or horizontally. When cutting horizontally (FIG. 3), the cutter blade is able to be pivoted in a horizontal plane about a vertical axis on a cutter support arm which produces an out of balance situation whereby the unit is unstable and can tip over, whether in use or at rest. A complex belt drive is required.
U.S. Pat. No. 2,618,919 (Hutchens) also discloses a single wheeled carriage arrangement with both a horizontally cutting trimmer blade 11 and a vertically cutting cutter blade 19. Each of these blades is able to be swivelled to a tilted position and independently operated so that two simultaneous inclined cuts or two simultaneous horizontal cuts are able to be achieved. This device is supported by a single wheel and a pair of short legs 31. The device has a conventional free standing and upstanding handle (of which only the shaft 29 is illustrated). The handle 29 is therefore presumed to be the then conventional T-shaped lawn mower handle. Each cutting blade, in order to swivel, is mounted on an outrigger journal. Except for the handle arrangement, the device is of very broad dimensions with the cutters extending a long way forward of the single wheel. This single wheel is placed approximately midway front to rear and approximately on the centerline of this carriage device to constitute both a front to rear and a left to right pivot point. However, the carriage has substantial masses located at some distance from the pivot or balance point. As a result, the device is unwieldy, being difficult to balance and therefore difficult to use.
U.S. Pat. No. 2,708,335 (Newton) also discloses a single wheel device which in this instance is able to cut both horizontally and vertically. The single wheel supports the motor and cutter blade while cutting vertically. It is not clear how the device is supported during horizontal cutting as illustrated in FIG. 5. In this device the handle 27 consists of a single bent tube and therefore it would be necessary for the operator to keep a very firm grip on the handle in order to prevent the device from twisting or tilting whilst cutting vertically. U.S. Pat. No. 2,653,381 (Rooke) discloses a similar device with a rod-like handle 27 which again has a single grip 43. A roller 36 supports the device whilst trimming vertically and the device appears to be supported by skids whilst cutting horizontally.
U.S. Pat. No. 4,033,098 (Green) discloses a device for cutting horizontally which has a single wheel 11 and a pair of spaced apart handles 33. As seen in FIG. 5, in order to cut grass adjacent a wall 42, it is necessary for the handles 33 to be released, then twisted to one side and then secured in that position in order that the operator""s hand not be scraped during the passage along the wall 42. Furthermore, because the large motor 12 is mounted forwardly of the wheel 11, the center of gravity of the device is forward of the wheel 11. Therefore, in operation it is necessary for the handles 33 to be forced downwardly in order to maintain the correct cutting height. If, during operation, the handles 33 are inadvertently released, then the cutting elements 28 immediately impact with the ground, which is extremely dangerous.
Another single wheeled device in which the center of gravity is forward of the single wheel is that disclosed in Australian Patent No. 107,917 (Collins and Henderson). This device has a cutting disc 4 which normally rotates in a horizontal plane above a pair of skids 16 which assist to support the weight of the device. The weight of the cutting arrangement means that the center of gravity of the device is forward of the wheel 2, notwithstanding that the engine 3 is mounted above, but just behind, the wheel 2. Again, in operation it is necessary for the operator to push down on the handles 13 in order to relieve the weight on the skids 16.
U.S. Pat. No. 4,845,929 (Kawasaki et al.) again discloses a device for cutting horizontally in which a pair of wheels is positioned inside a dome-shaped cutting disc. The wheels are pivotable about a vertical axis in order to permit cutting in different directions. In the second embodiment of FIGS. 19-23, the trimmer is supported by a pair of running wheels 8 and a skid 170 (column 12, line 37) but designated 156 in FIG. 20. This indicates that the center of gravity of the device is forward of the wheels 8 and therefore the guide handles 6 have to be depressed in order to operate the device.
Another example of a prior art brush cutting device using a nylon filament is a two wheeled device in essence similar to a rotary four wheel lawn mower with extended horizontal cutting disks but with only two rear wheels. The center of gravity is forward of the two wheels as the brush cutting head extends forward. Again, pressure has to be exerted downwards on the handles to lift the cutting head away from the ground. This type of unit is large and not easy to maneuver due to its bulk. The complete machine cannot be laterally tilted on its longitudinal axis to cut closely against a wall (when trimming along the wall) or along a footpath""s edge. This machine is commercially available in the USA being sold under the trademarks DR TRIMMER or DR MOWER and has a 6 horsepower engine. This category of trimming machines also cannot fit into a boot or trunk of even a large car, and requires a great deal of room for storage.
It is the object of the present invention to substantially overcome or ameliorate some of the above-mentioned disadvantages and problems by the provision of a powered cutting device which is steerable with both hands, able to be maneuvered in substantially the same fashion as a wheelbarrow, brush cutter, or stick edger, and able to either mow substantially horizontally or trim substantially vertically.
In accordance with the first aspect of the present invention there is disclosed:
a powered vegetative cutting device maneuverable in the manner of a wheelbarrow, brush cutter, or stick edger by a walking operator or operable to both substantially horizontally mow and substantially vertically trim vegetation, said cutting device including:
an elongated frame having handle means;
a power unit supported by said frame;
a rotatable vegetative cutter means; and
a power train interconnecting said power unit and said cutter means,
wherein said cutter means is movable between a mowing position in which it rotates about a substantially vertical axis and a trimming position in which it rotates about a substantially horizontal axis, a releasable latch means operatively associated with said power train and said frame for maintaining said cutter means in either one of said positions, and said power train including a power directing means operable to rotate said cutter means in each said position.
In one form, the handle means are at one, rearward, end of the frame, a ground engaging wheel means is at the other, forward, end of the frame, the cutter means is located forward of said wheel means, and the power unit is located intermediate said ends of the frame, thereby causing the center of gravity of said cutting device to lie between said handle means and said wheel means.
In another form, the power unit is located at one, rearward, end of the frame, the cutter means is located at the other, forward, end of the frame, and the handle means are located intermediate the power unit and the cutter means.
The cutting device preferably includes a ground engaging wheel means located rearwardly of the cutter means.
The power directing means is preferably located within a flexible boot.
In an embodiment, the power directing means comprises a universal joint.
In another embodiment, the power directing means comprises a pair of gimbals pivotally connected together, each gimbal having a shaft rotatably mounted therein, one of said shafts being driven by said power unit, the other of said shafts driving said cutter means, each of said shafts having one of two intermeshed bevelled crown gears at its free end, and the angle between said shafts being adjustable by said gimbals pivoting relative to each other.
The releasable latch means preferably comprises a slotted link member fixed to one of said gimbals, a split sleeve enveloping part of the other of said gimbals and said frame, and clamping means passing through said link member and split sleeve to clamp said other gimbal, frame and link member together.
The cutter means preferably comprises a pair of nylon filaments.
The cutting device preferably includes a filament guard mounted adjacent to said cutter means and between said cutter means and said handle means, said filament guard being movable with said cutter means between said mowing and trimming positions.
The cutting device preferably includes height adjustment means to vary the height of said cutter means above said ground engaging wheel means.
The power unit is preferably an internal combustion engine or electric motor.
In accordance with a second aspect of the invention there is disclosed a method of cutting vegetation comprising the steps of:
a. using a powered cutting device steerable in the manner of a wheelbarrow, brush cutter, or stick edger by a walking operator and having a cutter means and handle means grasped by said operator, to mow an area of vegetation with said cutter means rotating about a substantially vertical axis;
b. moving said cutter means so that it rotates about a substantially horizontal axis; and,
c. using said power cutting device to vertically trim at least a portion of the periphery of said area of vegetation.
In accordance with a third aspect of the invention there is disclosed a method of cutting vegetation comprising the steps of:
a. using a power cutting device steerable in the manner of a wheelbarrow, brush cutter, or stick edger by a walking operator and having a cutter means and handle means grasped by said operator, to vertically trim at least a portion of the periphery of an area of vegetation with said cutter means rotating about a substantially horizontal axis;
b. moving said cutter means so that it rotates about a substantially vertical axis; and,
c. using said powered cutting device to mow said area of vegetation.
Both methods preferably include the step of laterally tilting said handle means whilst trimming to tilt said substantially horizontal axis.
Preferably, the cutting device can be operated without tiring the operator. The cutting device has a negligible turning circle, is able to be tilted easily to either side, and its frame supports a substantial part of the weight of the powered cutting device. In addition, the cutter means is able to follow the surface, should it be undulating, without upsetting the stability of the machine. The cutting device is also preferably able to be placed in an operational rest position, either voluntarily or in an emergency, with the cutter means always remaining above the ground surface.